Wheel drive for tracked vehicles

ABSTRACT

A wheel drive for working machines, in particular tracked vehicles. A drive shaft (6) connects a hydraulic motor (26), which is in the form of a slow-running radial piston engine, to a planetary gear (11, 40). The hydraulic motor (26) is disposed on one side of a hub carrier (4) and the planetary gear (11, 40) and a hub (1) are disposed on the other side. A sliding ring seal (21) is arranged between the hub carrier (4) and the hub (1).

The invention concerns a drive device for working machines, inparticular for tracked vehicles such as bulldozers or the like.

Multiple developments of a tumbler drive are to be regarded as knownfrom the prior art. In said drive devices, a hydraulic motor drives achain gear via a planetary gear. The drive device should have smalldimensions, especially in axial directions, so as not to project overthe width of a chain tractor, such as a crawler excavator. The planetarygear must have a sufficiently great ratio in order to obtain a low speedlevel on the chain gear. The drive device must be provided with a braketo firmly brake the output during still stand of the hydraulic motor.Since the drive device is used even under extreme external conditions,provision must be made for a reliable seal over a long service life.Finally, the drive device must be easy to assemble and to maintain.Considering the production costs, the number of parts of the drivedevice must be as small as possible.

The above mentioned requirements are not met by the known drive devices.When the hydraulic motor is designed as an axial piston machine with ahelical-disc construction, for example, an axially short design can beobtained only when said axial piston machine is integrated in the hubcarrier. Examples of this are found in DE-A 27 44 936, DE-A 28 31 458and DE-A 42 35 697. As a rule, the speeds of the hydraulic motor are sohigh that a multi-stage planetary gear has to be used. This multi-stagecondition generally increases the axial length of the drive device sothat the advantage obtained with the integration of the hydraulic motorin the hub carrier hydraulic motor integrated in the hub carrier is thatbearings of large dimensions must be used for supporting the hub uponthe hub carrier. To this disadvantage is added another: since the hubmust be sealed relative to the hub carrier, seals with equally largediameters are needed. These circumstances result in a cost increase. Inaddition, the service life of the seal suffers by the relatively highperipheral speeds.

Although radial piston engines have long been known to the expert (see,for example DE-A 15 28 519 and DE-A 22 55 239), until today they havenot been used in combination with a brake and a planetary gear as atumbler drive for tracked vehicles.

The problem, on which this invention is based, is to provide a drivedevice for use in tracked vehicles which, in particular, stands out by adesign that is of moderate cost, compact, simple to assemble andreliable.

The problem, on which the invention is based, is solved by a drivedevice having the characteristics stated in the main claim.

Compared to the tumbler drives known already, the solution according tothe invention is surprisingly an extraordinarily simple design. The slowrunning radial piston engine works at a speed level which does not makenecessary any multi-stage planetary gear. In addition, this engine,conditioned by the system, consists of relatively few parts. It isdesigned compactly, in an axial direction, so that it can be directlymounted upon one side of the hub carrier. A drive shaft connects thecylinder block of the radial piston engine with the planetary gear, theoutput member of which is non-rotatably connected with the hub.

Advantageous developments of the drive device, according to theinvention, can be understood from claims 2 to 5.

Other features essential to the invention, and the advantages resultingtherefrom, are to be understood from the explanation of two embodimentsthat follows. In the drawings:

FIG. 1 shows, in a simplified representation, a first embodiment of adrive device, in particular for a tracked vehicle; and

FIG. 2 shows another embodiment which differs, in particular, from thearrangement of FIG. 1 by the structure of the end output.

The drive device reproduced in FIG. 1 in a longitudinal section and asimplified representation, is especially adequate for the drive of achain gear of a tracked vehicle such as a bulldozer or the like. It is adrive device which is also familiar by the designation of a tumblerdrive.

A chain gear, itself not reproduced, is non-rotatably connected with arotatingly disposed hub 1. For the non-rotatable connection, the hub 1has a multiplicity of bolt holes 2, on its periphery, which accommodatestud bolts, likewise not shown, of the chain gear.

The hub 1 is rotatably situated upon a stationary hub carrier 4 via twotaper roller bearings 3. The taper roller bearings are assembled in an 0arrangement. The hub carrier 4 is firmly connected with the vehiclechassis which cannot be understood in detail from the drawing, but isfamiliar to the expert. Several bolt holes 5 are distributed on theperiphery of the hub carrier 4 for the firm connection of the hubcarrier 4 with the vehicle chassis.

In the stationarily disposed hub carrier 4, a drive shaft 6 isnon-rotatably supported via a single bearing, especially a taper rollerbearing 7. A connecting shaft 8 joins up with the drive shaft 6. Thenumeral 9 marks the separation between the drive shaft 6 and theconnecting shaft 8.

The drive shaft 6, floatingly supported on one side, is non-rotatablyconnected at its free end-lying to the left in the drawing-with aninternal central gear 10 (sun) of a planetary gear 11. The internalcentral gear 10 can be made integral with the drive shaft 6, as in thepresent case. The internal central gear 10 is in constant teeth meshingwith planetary gears 12 of which one is reproduced. The planetary gears12 are rotatably supported via anti-friction bearings 13 upon one web 14of the planetary gear 11. The web 14 is an additional component part ofan end output housing 15 which is snugly and firmly bolted with the hub1 and surrounds the planetary gear 11.

In addition, the planetary gears 12 are in constant teeth meshing with astationary external central gear 16 (hollow gear) of the planetary gear11. The external central gear 16 is non-rotatably slipped on the hubcarrier 4 in the area of a spline 17 and locked by a nut 18, in an axialdirection, against a shoulder of the hub carrier 4 via the taper rollerbearings 3.

Since the hub 1 rotates opposite the stationary hub carrier 4, a radialgap 20 results between said parts. Since the end output housing 15 is atleast partially filled with lubricant and coolant, a suitable seal mustexist which holds back the coolant and lubricant and protects theinterior of the end output housing against external influences. A slidering seal 21 assumes said task. Said slide ring seal 21, of a knownconstruction, consists of a rotating slide ring 22, a first sealing ring23 inserted in a recess of the hub 1, a stationary counter ring 24 and asecond sealing ring 25 inserted in a recess of the hub carrier 4. It isshown in the drawing that the slide ring seal 21 has an effectivediameter which is only slightly larger than the external diameter of thetaper roller bearings 3.

A hydraulic motor 26 completes the drive device. It is of the essencefor the drive device that said hydraulic motor consist of a slow runningradial piston engine. The absorption volume of the radial piston engineamounts to approximately 1 180 cm³. The maximum speed is about 3101/min. The hydraulic motor is switchable, it being possible for theratio of the absorption volumes to be q_(min) /q_(max) =0.33/0.50/0.66.The brake valves are on the hydraulic motor. The hydraulic circuit isopen.

A cylinder block 27 is non-rotatably connected by a spline section 28with the drive shaft 6. Similar to this, a non-rotatable connectionbetween the cylinder block 27 and the connecting shaft 8 exists via ageometrically equally designed spline section 29.

In a manner known per se, several pistons 30 are radially movablysupported in the cylinder block 27. They support themselves via rollers31 on a stationary cam 32. The hydraulic fluid is supplied and removedby a distributor 33. A housing 34 surrounds the radial piston engine andis, the same as the cam 32, screwed onto the hub carrier 4. For thispurpose, several bolt holes 35 are provided in the hub carrier 4.

The connecting shaft 8 is axially movably disposed. On one side, it isunder the action of a compression spring 36 and, on the other, a forceacts upon it which depends on the pressure prevalent in a pressurechamber 37. In the plotted end position (left) shown of the connectingshaft 8, the pressure prevalent in the pressure chamber 37 is high sothat a clamping brake 38 is disengaged. In another case, said clampingbrake 38 is engaged by the force of the compression spring 36. Theclamping brake 38 acts as parking brake during stand still of thevehicle.

The tumbler drive, explained as having a slow running radial pistonengine and a one-stage planetary gear, makes it possible to drive achain gear at a ratio as high as possible. The tumbler drive is designedwith regard to the space requirement-calculated on the hub carrier4-substantially symmetrically. This means that on one side, the hub 1,the planetary gear 11 and the hydraulic motor 26 are mounted and, on theother side, are rotarily driveably situated. The drive shaft 6 forms theoperable connection between the radial piston engine and the planetarygear 11. An essential advantage of said connection is that the diametersof the drive shaft 6 and of the hub carrier 4 can be kept small in thearea of said connection. From this it results that the diameters of thetaper roller bearings 3 are also small. Accordingly, the radialdimensions of the slide ring seal 21 are also small. Since theperipheral speeds are also relatively low too, on account of theprevailing diameter ratios and of the relatively low speed level, areliable seal with a long service life results. In addition, the drivedevice is built compact and is characterized by very smooth running. Theplanetary gear can work with straight or helical cut gears.

The longitudinal section of a tumbler drive reproduced in FIG. 2,likewise in a simplified representation, has fundamental features incommon with the drive device of FIG. 1. Therefore, corresponding partshave been provided with corresponding reference numerals.

When work is to be carried out with separate oil supplies, an additionalseal 39, for example, a radial shaft seal, can rotate upon the driveshaft 6. An essential difference from the above explained embodimentconsists in that the web 14 of the planetary gear 40 is non-rotatablyconnected, via the spline 17, with the hub carrier 4. Accordingly, theweb 14 in this drive device is not a component part of the end outputhousing 15. Rather the external central gear 16 is a component part ofthe hub 1 as an output member of the planetary gear 40. The end outputhousing 15 is accordingly formed by the hub 1 and an additional lid 41.This modified embodiment can, in particular, be advantageously used whenthe speed level on the output side is so low that it is possible torenounce to the maximum possible ratio (like in the embodiment of FIG.1).

Reference numerals

1 hub

2 bolted hole

3 taper roller bearing

4 hub carrier

5 bolted hole

6 drive shaft

7 taper roller bearing

8 connecting shaft

9 separation

10 internal central gear

11 planetary gear

12 planetary gear

13 anti-friction bearing

14 web

15 end output housing

16 external central gear

17 spline

18 nut

19 shoulder

20 gap

21 slide ring seal

22 rotary slide ring

22 rotary slide ring

23 sealing ring

24 stationary counter ring

25 sealing ring

26 hydraulic motor

27 cylinder block

28 spline section

29 spline section

30 piston

31 roller

32 cam

33 distributor

34 housing

35 bolted hole

36 compression spring

37 pressure chamber

38 clamping brake

39 seal

40 planetary gear

41 lid

I claim:
 1. A wheel drive for a vehicle consisting of a hydraulic motor(26) which, via a drive shaft (6), actuates an inner central gear (10)of a planetary gear (11, 40) and an output member (web 14 or externalcentral gear 16) which is non-rotatably connected with a hub (1)supported on a stationarily situated hub carrier (4);wherein said driveshaft (6) is floatingly supported on said hub carrier (4), saidhydraulic motor (26) is a slow running radial piston engine and ismounted, in a longitudinal direction of the vehicle, on one side of saidhub carrier (4), while said planetary gear (11, 40) and said hub (1) aresituated on another side of said hub carrier (4), and a slide ring seal(21) is disposed between said hub carrier (4) and said hub (1).
 2. Thedrive device according to claim 1, wherein said external central gear(16) is non-rotatably connected with said hub carrier (4) and saidoutput member is formed by said web (14) of said planetary gear (11),which is firmly connected by an end output housing (15) with said hub(1).
 3. The drive device according to claim 1, wherein said web (14) ofsaid planetary gear (40) is non-rotatably connected with said hubcarrier (4), while said output member is formed by said central gear(16) non-rotatably connected with said hub (1).
 4. The drive deviceaccording to claim 1, wherein said slide ring seal (21) furthercomprises a rotary slide ring (22), a sealing ring (23) inserted in arecess of said hub (1), a stationary counter ring (24) and a secondsealing ring (25) inserted in a recess of said hub carrier (4).
 5. Thedrive device according to claim 1, wherein a clamping brake (38) iscoordinated with said hydraulic motor (26).